At present, the problem of diagnostics of malignant neoplasms, especially at early stages, is of vital importance in oncology. In spite of an extensive use of histological analytical methods, great successes of ultrasonic and X-ray diagnostics, in spite of great progress achieved in endoscopic examination methods, as well as in X-ray and nuclear magnetic resonance (NMR) tomography, the sensitivity, accuracy and availability of these methods still remain inadequate. One of the promising trends for perfecting the diagnosis of malignant tumours resides in the use of contrasting agents capable of being selectively accumulated in such tumours. It is a well established fact, for instance, that malignant tumours accumulate some dyes at elevated concentrations as compared to healthy body tissues, and this fact is used for fluorescent diagnosis of tumours using the fluorescence characteristic of a dye accumulated therein.
Various compositions, such as, antibiotics of the tetracycline group, have been used as fluorescent contrasting agents. One of the diagnostic methods made it possible to detect stomach cancer at late IIIrd and IVth stages of the disease, however, with a degree of precision found insufficient for diagnostic purposes (Cf. I. Klinger, K. Katz. Gastroenterology, enterology, 1961, 41, 29-32). Use of endoscopic technique, in combination with fluorescent contrasting tetracycline agents (Cf. I. Ya. Barsky, G. V. Papayan, V. V. Shchedrunov and Yu. A. Glukhir Luminescent Analytical Methods in Medical and Biological Examinations, (a collection of publications), Riga, 1983, pp. 182-189) has also demonstrated poor reliability in diagnostics of tumours because of blurred contrast in which tetracycline accumulated in malignant tissues stands out as compared to healthy tissues.
Fluorescent contrasting using fluorescein as a dyeing agent has been used for detecting metastases into regional lymph nodes in larynx cancer (Cf. S. I. Mostovoy, J. of Disorders of the Ear, Nose and Throat, 1961, No. 4, pp. 34-36). It has been stated that not only cancer-affected lymph nodes, but also other body organs exhibited bright fluorescence, and this fact renders the method unsuitable for diagnostics. Some other authors also have arrived to the same conclusions (Cf. G. E. Moore, Science, 1977, 106, 130-131; F. H. I. Figge, G. S. Weiland, L. O. I. Manganiello, Proc. Soc. Exper. Biol. Med., 68, 640-641, 1948).
For contrasting malignant growths, attempts have been also made to use a contrasting agent containing, as a contrasting substance, fluorescin and used either in the form of a 20%-solution for intravenous administration in 2 to 5 ml doses, or in the form of 1 gr of powder washed down with soda water (Cf. Yu. N. Yefuni, Vestnik Otorhinolaryngology [in Russian], 1961, No. 2, pp. 11-15). The disadvantage of the latter contrasting agent lies in poor contrast offered by fluorescein accumulated in a malignant tissue as against a healthy tissue, whereby the accuracy of diagnostics is affected. The degree of contrast offered by fluorescein accumulated in a malignant tissue versus that accumulated in a normal body tissue has been assessed in terms of a ratio of the concentrations of fluorescein contained in these two types of tissues per gram of the tissue weight. According to the prior art, the reliability of fluorescent diagnostics of, e.g. malignant growths in the organs of the upper respiratory tract, was 30%. Accordingly, an inference may be arrived at that epithelial malignant tumours do not fluoresce, i.e. they do not accumulate fluorescein.